In various types of molding machines such as injection-molding machines and press-molding machines and processing apparatus such as bonding machines (industrial machines and processing machines), an electric mechanism (mechanical driving section) is driven by a motor to apply a pressure to a pressurized target. In the processing apparatus described above, an actual pressure value, which is a pressure value obtained when a mechanical load is pressed against a molding material or a work piece which is the pressurized target, is detected as a pressure detection value. Based on the pressure detection value and a pressure command value, a pressure control computation defined by a parameter is performed. The parameter as used herein is a parameter such as a gain in the pressure control computation.
It is necessary to appropriately adjust the parameter for the pressure control computation. When the parameter is too large, the stability of a control system is impaired, resulting in instability of the control system or occurrence of a vibration phenomenon in which a high-frequency micro-vibration is superimposed on the pressure applied to the pressurized target. By the transmission of the micro-vibration generated by the vibration phenomenon to the work piece or the like, the result of processing is adversely affected.
On the other hand, when the parameter is too small, a phenomenon in which long time is required to achieve a target pressure value (pressure command signal) or the like is brought about. When an external disturbance is applied, there is a fear in that the external disturbance cannot be sufficiently removed. In particular, a compensation for the external disturbance cannot be performed only by feedforward control for operating the motor based not on both the pressure detection value and the target pressure value but only on the target pressure value. The removal can be performed only by performing the pressure control computation based on the pressure detection value and the target pressure value to perform the operation of the motor. Therefore, it is important to appropriately adjust the parameter of the pressure control computation.
Moreover, for example, in the case of a conventional apparatus described in Patent Literature 1, in pressure control in which a pressure deviation (difference) between the pressure detection value and the target pressure value is multiplied by a pressure gain to determine a speed command of the motor and a speed control computation is performed to follow the speed command, an elastic constant of the pressurized target is obtained by a calculation and is then divided by a predetermined proportionality constant to calculate a pressure gain.